Previously, to produce items having an image disposed on one or both sides of the item, using a plastic or other suitable material, required the use of different and multiple processes. For example, a sheet of material or fluid material from which an item was to be formed might be initially positioned within or directed into an injection or compression molding device in order to create detail or features required on at least one side of the item. Subsequently, the material sheet would then be positioned or run through a suitable second thermoforming device to complete the formation of the item from the material. The resulting thermoformed item might then be heat treated under vacuum conditions with a dye printing sheet to print a selected pre-drawn design or image onto a surface of the item.
However, these multi-step processes have a number of significant drawbacks. First, the added steps typically slow production time and increase production cost. Second, subjecting the item to repeated high-temperature steps can have a detrimental effect on the item. Additionally, such printing was traditionally applicable to a limited number of suitable materials, such as thermoplastics, metals, and the like with a smooth, non-textured surface.
As to the first point, to initially print the detailed design on an item, the process may require both a detail molding device and step, which can be either an injection molding step or a compression molding step, as well as a final thermoforming step (e.g., melting or sublimation techniques) used to create the final form for the item. Finally, the pre-drawn design needs to be imprinted to the item. The multiple steps and molding devices required for each step significantly increases the complexity of the process and the costs for producing the final item with an image or design printed thereon.
Of no less importance is the integrity of the final item. That is, when a sheet of material is positioned within the heat treatment device to finalize the transfer of the dye printing onto the item, often times the process results in a partial or complete deformation or destruction of the original detail from the initial thermoforming steps. That is, due to the repeated use of high-temperatures necessary to initiate transfer of the dye from a pre-printed film to one or both sides of the thermoformed item, the edges around the item may be unable to withstand such heat for the required duration of the transfer process. However, shortened heat transfer times would fail to ensure consistent transfer of the dye on the entire surface of the item. Thus, the resulting item may often be undesirable or unusable for its intended purpose due to the damage done to the thermoform details on the item.
Finally, the use of materials which are not traditionally suitable for printing, such as wood, rubber, cellulosic material, and the like, require attachment of labels, tags or other similar devices. Even thermoplastic materials with textured surfaces may present difficulties for printing operations.
Therefore, it is desirable to develop a method for effectively transferring an image from a printing sheet to a surface of an item made from most any material and in a single heat transfer step.